Hidden indica on household and other useful articles has been known and used in the past, however, this usage has been limited to the utilization of special chemicals or water actuated dyes that produce a permanent image. Some prior art systems with expensive or even caustic developers have been utilized in order to produce the hidden indica into a readily visible display. This method is often undesirable, particularly where the indica is to be used in conjunction with small children or if the product is distributed to the masses.
The use of water as a developer has also been practiced in prior art, however, the novelty is easily understood and lacks intrigue for a hidden message as it remains in the fabric until the medium is completely dried. Other methods transform the indica into a visible message by the application and combination of one element to another.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention. However, the following United States patents are considered related and indicative of the state-of-the art:
______________________________________ PATENT INVENTOR ISSUED ______________________________________ 3,989,279 Levy 2 November 1976 3,139,689 Quintel, et al 7 July 1964 481,023 Gruene 16 August 1892 ______________________________________
The Levy patent discloses a hidden indica that is imprinted onto a carrier such as a tea bag with a wax base marking pencil, or a suitable non-toxic ink. The tea in the bag provides the staining agent so that introduction of the tea bag into boiling water will provide a stain which will discolor the carrier, or tea bag, with respect to the indica which does not discolor. This selective staining of one of the surfaces of the carrier provides the contrast between the indica and the carrier to make the indica visible. It will be noted that this prior art uses only surface staining with no color nor visible marking on the bag, allowing the area around the indica to create the contrast.
The Quintel patent discloses a method where indica is printed on a card with an invisible substance, such as a diluted lacquer more commonly known as invisible ink. Inasmuch as the substance is absorbed and is the same shade of coloring as the card, it is only rendered visible when a treatment is deployed to obtain a distinct contrast between the substance and the card, as an example, by moisture or liquid applied to the zone. This is accomplished in this invention using water as the moisturizing agent with a wick disposed over a receptacle extended therein for wetting and actuating the hidden indica. This indica is capable of being rendered visible by moisture applied onto the zone but also retains this visibility only while wet and remains in this state until the card upon which this is printed becomes dry by natural vaporization of the liquid into the air.
The Gruene patent discloses a transparent toy or puzzle picture with the image found on a surface of glass. The exterior is covered with powdered silicate of magnesium that is rubbed into the surface while the image or writing is covered with a material that does not allow the surface to be affected. This material is removed after the magnesium has etched the glass sufficiently. The indica is then visible when moisture is applied to the glass surface, such as being breathed upon by the user. Another application of Gruene's invention is using two similar glass plates treated in the above described manner with one placed on top of the other. This allows the moisture in the plate to remain with the picture or indica visible for a longer period of time than when applied to the top plate only.